In many industrial, domestic or other situations, it is desirable to present a clear message concerning ambient physical conditions. Such physical conditions may include temperature, pressure, and humidity. It is desirable to convert detected values into a form that is readily comprehensible to a human viewer.
JP2006194366A2 discloses a temperature indicator for use with water pipes with a low temperature and high temperature display connected to either end of a movable component that is connected to temperature reaction component inside a case. The temperature indicator comprises a case attached to an object to be measured; a temperature responsive actuating member of which one end side is attached to the inside of the case and which is contracted or expanded depending on temperature change. The indicator further comprises a movable actuating member attached to the other end side of the temperature responsive actuating member and displaced in the axial center direction of the case by contraction or extension of the temperature responsive actuating member; a low-temperature display part attached to one end side of the movable actuating member, and protruded from the case when the temperature becomes below predetermined low temperature. The indicator further comprises a high-temperature display part attached to the other end side of the movable actuating member, and protruded from the case when the temperature exceeds predetermined high temperature. The temperature indicator also comprises a partition wall (excessive expansion preventive member) preventing expansion of the temperature responsive actuating member above a certain level.
EP0126983A1 discloses an encapsulated thermometer. The thermometer comprising an expansion box which acts on one of two connecting rods of a parallelogram linkage and thus moves an indicator plate along the inside of a transparent calibrated lid. The individual temperature regions to be displayed are represented by coloured symbols which form an optical translation of the movement of the pointer.
A drawback of these described approaches is the graphical poverty of the information presented to the viewer and the inherent need to divide the display area as a whole into separate areas for each possible display value.
Other prior art solutions may be based on temperature sensitive liquid crystal pattern. However, these are associated with prohibitive limitations in terms of temperature range, size, etc.